Engine stop device



June 17, 1952 F. J. sT. LUCAS ENGINE STOP DEVICE Filed June 30, 1950 Fie.1

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Frank J. St. Lucas, Omaha, Nebr.

Application June 30, 1950, Serial No. 171,321

This invention relates to'an engine stop device. Specifically it relates to a stop device actuated by the pressure in the crankcase of a compression-ignition engine.

It is well known that damaging crankcase explosions have occurred in compression-ignition engines, particularly diesel engines. The exact cause of these explosions cannot be stated with certainty, but they have been ascribed to faulty pistons or piston blow-by. Applicant has discovered that such explosions are commonly preceded by the development of abnormal pressures in the crankcase. Thesepressures are not high enough to be harmful to the engine. This discovery inspired the invention herein described.

A second consideration taken into account by applicant is the desirability of stopping the engine should an explosion occur. Not infrequently minor damage done by such an explosion is increased by the continued running of the damaged engine.

The device comprises a pressure actuated motor which operates a stopping mechanism and in the preferred form this comprises a switch in an electric circuit. The circuit controlled by the switch includes some type of fuel cut-off device which acts either on the governor, or injector control racks or the fuel pump driving means to shut off the fuel supply.

It is, of course, imperative that a safety device be reliable in its operation. As a convenient way of checking the safety device to see that it is operating correctly, a secondary pressure source may be placed selectively in communication with the pressure motor. The pressure available from the secondary source approximates the maximum permissible crankcase pressure and will cause the device to operate to stop the engine if the device is in proper working order. A convenient secondary source of pressure is the scavenging air chamber of the diesel engine.

A preferred embodiment of the invention is shown in the accompanying drawing in which:

Fig. 1 is a sectional view of a device embodying the invention.

Fig. 2 is a simplified schematic showing of an electric circuit controlled by the pressure actuated motor.

Referring first to Fig. 1, a portion of a diesel engine is indicated at 5, and includes a crankcase, a portion of which appears at 6 and a scavenging air chamber, a portion of which appears at 1. A pipe 8 leads from the crankcase 6 to a T connection 9. A stop valve ll con- 3 Claims. (01. 123-198) trols the flow of fluid through the pipe 8. A second pipe I2 leads to the T connection 9 from the scavenging air chamber 1 and flow therethrough is controlled by a stop valve l3. A pipe [4 leads from the T connection 9 to the motor means generally indicated at I5. Any conventional valve means whereby pipe 8 or pipe I2 may be placed selectively in communication with pipe M could be substituted for stop valves H and l3.

The pressure actuated motor comprises a divided housing having upper and lower portions l6 and I '1 respectively. A slack diaphragm I8 is disposed between these portions 16 and I1. Bolts [9 pass through holes in the flanges 2| and 22 of the portions I6 and I1 and through holes in the periphery of the diaphragm 18.

A box-like extension 23 open atthe top is formed on the portion [6 and is provided with a removable cover plate 3!. The extension 23 provides an isolated space in which a switch 24 is mounted. An actuating member 26 is reciprocable in a guide 25 formed in the portion IS. A combination thrust and motion limiting plate 21 is provided beneath the diaphragm l8 and is secured to the member 26 by a screw 28. The upper end of the member 26 is arranged to engage the actuating element 29 of the switch 24.

A sleeve bushing 32 is adjustable relatively to the cover plate 3! and may be secured in place by locking nuts 33. A reset member 34 is reciprocable in the bushing 32. A spring 35 biases the member 30 to its upper position as shown in Fig. 1.

The space above the diaphragm I8 is in free communication with the atmosphere through the air vent 36.

As shown in Fig. 2, the switch 24 controls a circuit which includes a source of electric power typified by the battery 31 and the engine stopping means which is indicated by the legend. This engine stopping means may be one of a variety of types well known in the art.

The circuit when opened by switch 24 may serve to deenergize the clutch coil of an electric governor which will operate to move the fuel racks to no fuel or stop position, or it may deenergize the electro-magnet coil of a pneumatic governor with the resultant fuel cut-off. If the fuel pump is driven by an electric motor, the switch 24 may serve to stop the motor thus cutting off zthe fuel supply. These engine stopping means are Well known in the art, and the examples cited are merely illustrative of stopping means which will readily suggest themselves to a develop in the crankcase, the diaphragm [8 will be raised against its own weight and that of the member 26. The upward motion of the member 26 causes it to move the actuating element 29 of the switch 24. The switch 24 is preferably of the toggle or snap-acting type, so that its operation is positive. When the switch element 24 is snapped, the circuit is opened whereby the engine stopping means is operated to stop the engine. The safety device will remain in stop position until the pressure returns to normal in the crankcase and until the switch is reset by pushing the reset member 34.

The operation of the safety device maybe checked by closing the valve H and opening valve 1 t admi tins scav n in a r. w ich is n e res u n a diesel en ne. t the motor means I5. The scavenging,airpressure approximates the maximum desirable crankcase pressure and will act to stop the engine. If the engine does not stop, the operator will check the safety device.

The weight of the member 26 serves to bias the diaphragm against the pressure acting thereon. Any suitable biasing means could be substituted.

It will be apparent that an explosion would also operate the safety device to stop the engine, whereby the damage occurring subsequently to the explosion will be minimized.

.31) The invention has been described as used with electrically operated engine stopping means. This is the preferred form because of its simplicity; it will be apparent that the presengine having a crankcase;

sure actuated motor could also be used to operate any engine stopping means, e. g. a mechanical device.

I claim:

1. The combination of a compression-ignition engine having a crankcase; motor means adapted to move in response to a predetermined positive pressure in said crankcase; and engine stopping means adapted to be put into action by movement of said motor in response to said predetermined pressure.

2. The combination of a compression-ignition motor means adapted to move in response to a predetermined positive pressure; a secondary source of fiuid under a pressure slightly in excess of said predetermined positive pressure; inlet means to said motor adapted to admit fluid selectively from said crankcase or from said secondary source; and engine stopping means adapted to be put into action by movement of said motor in response to said. predetermined pressure.

3. The combination defined in claim 2, said engine having a scavenging air chamber, said chamber serving as said secondary source of fluid.

FRANK J. ST. LUCAS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

